Titration apparatus



March 30, 1965 R. HEISS 3,175,734

TITRATION APPARATUS Filed Dec. 3, 1962 INVENTOR.

EM A 00/5 /8 H E 155 ATTORNEY United States Patent 3,175,734 'liTRATIONAPPARATUS Louis R. Heiss, Silver Spring, Md assignor to Americaninstrument Company, Inc, Silver Spring, Md. Filed Dec. 3, 1962, Ser. No.241,575 8 Claims. (ill. 222-481) This invention relates to titrationapparatus, and more particularly to a burette or titration device havingreadily interchangeable pipette elements.

A main object of the invention is to provide an improved titrationapparatus arranged for easy and rapid changing of its pipette andplunger elements, whereby the same main titration apparatus may be usedfor accurately dispensing different reagents, as required, by merelychanging its pipette and plunger subassembly, and whereby there is norisk of contaminating 'the reagent with which the device is employed bythe presence of material employed in a previous use of the apparatus.

A further object of the invention is to provide an improved automatictitration apparatus provided with means for easily and quickly changingits plunger and pipette elements, the apparatus being simple inconstruction, being compact in size, and being easy to manipulate.

A still further object of the invention is to provide an improvedburette or titration device having readily interchangeable pipette andplunger elements, the device being durable in construction, beingrelatively inexpensive to manufacture, and permitting differenttitrations or liquid dispensing operations to be performed in rapidsequence and with high accuracy.

A still further object of the invention is to provide an improvedchangeable plunger and pipette subassembly for a burette or titrationapparatus, said subassembly being easy to handle, being quickly andeasily replaceable without requiring tools or complex manipulations, andinvolving only a few simple and easily manufacturable parts.

Further objects and advantages of the invention will become apparentfrom the following description and claims, and from the accompanyingdrawings, wherein:

FIGURE 1 is a front elevational view of an improved automatic titrationapparatus constructed in accordance with the present invention.

FIGURE 2 is a vertical cross-sectional view taken substantially on line2-2 of FIGURE 1.

FIGURE 3 is an enlarged fragmentary elevational view of a removablepipette and plunger subassembly employed in the titration apparatus ofFIGURES 1 and 2.

FIGURE 4 is a top plan view of the assembly shown in FIGURE 3.

Referring to the drawings, 11 generally designates an improved titrationapparatus constructed in accordance with the present invention. Theapparatus 11 is of the automatic type similar generally to the apparatusdisclosed in US. Patent No. 2,925,198 to Sidney Healey. Said apparatuscomprises a vertical generally L-shaped plate 15 having the dependingarm 16 and the horizontally extending top arm 17. Secured to plate 15 isa housing 18 which includes a horizontally extending top portion 19 andan integral depending tubular vertical portion 21 A reversible electricmotor 32 is mounted on plate portion 16 and is drivingly connected to ahorizontal worm shaft 22 journalled in housing top portion 19, said wormshaft carrying the worm 23 which meshes with a worm wheel 24 journalledvertically in and rotatably supported in housing portion 19, said wormwheel having an internally threaded hub which is threadedly engaged withthe externally threaded shank 26 of a vertical driving plunger member25. Said plunger member is axially positioned in the vertical tubularhousing portion 20, and the enlarged lower portion of the plunger memheris formed with a frusto-conical bore or recess portion 27.

A radially extending horizontal guide pin 28 is secured to the enlargedlower portion of plunger member 25 and extends slidably through avertical guide slot 29 formed in the depending vertical tubular housingportion 20.

Designated at 30 is a generally L-shaped plate member which isvertically secured to housing portion 19 at its top end and which issecured to the lower margin of plate portion 16 at its bottom end, as bytransverse bolts 31 provided with spacer sleeves 21 between plate member3%) and plate portion 16 so that plate member 30 is secured in parallelreationship to plate portion 16. Mounted on plate member 30 are therespective upper and lower mircoswitches 76 and 77 connected to controlthe energization of the motor 32 in the manner described in theabove-mentioned prior Patent No. 2,925,198. A two-pole three-positionswitch 86 is mounted on plate portion 16 and a speed-controlpotentiometer 84 is mounted on the lower portion of plate member 30, theswitch 86 and potentiometer 84 being connected in circuit with themicroswitches 76, 77 and the reversible motor 32 in the manner describedin the aforesaid prior patent to control the vertical movements ofplunger member 25. Plate member 30 is formed with a vertical slot 73through which pin 28 projects so that it is engageable with theoperating arms of the microswitches 76 and 77 at the upper and lowerlimiting positions of plunger member 25. With switch 86 operated in onedirection, the motor 32 will be energized in a direction to move plungermember 25 downwardly, and the downward movement of said plunger memberwill continue until pin 28 engages the operating arm of lowermicroswitch '77, thereby opening the motor circuit. Conversely, theswitch 86 may be operated in the opposite direction causing the motor tobe energized in the reverse direction and to move plunger member 25upwardly until pin 28 engages the operating arm of the upper microswitch76, which again breaks the motor circuit. Switch 86 is normally in anopen-circuit position, as described in the afore-mentioned prior PatentNo. 2,925,198.

A counter 40, provided with a resetting knob 41, is mounted on plateportion 17 and is connected to worm shaft 22 through a coupling 42.

Designated generally at 43 is a replaceable titrant reservoir assemblyof the displacement type comprising a plunger element 44 which extendsinto and is moveable axially in the bore portion of a dispensing pipette45. The plunger element 44 is sealingly slid-able through an annularTeflon sealin ring 86 which is clamped between a rigid washer 81 and theflanged top rim 46 of the pipette. A resilient O-ring 82 is providedbeneath top rim 46 and another resilient O-ring 83 is provided in anannular groove formed in the underside of the yieldable Teflon sealingring 89, said Owing 83 engaging the rigid top rim 46. The sealingassembly comprising the members 81, 86,63, 46 and 82 is sealinglyclamped in the externally threaded enlarged lower portion of a bushingmember 47, by means of an externally knurled annular cup-shaped clampingring 68 threadedly engaged on the enlarged lower portion of bushingmember 47, as shown in FIGURE 2.

The upper portion of bushing member 47 is formed with a generallyL-shaped slot 48 open at its top end. Secured in the lower end portionof tubular housing member 20 is an inwardly projecting locking pin 49which is engageable in slot 43 and which cooperates with the horizontallower portion thereof to releasably retain the assembly 43 in the bottomend of housing member 20.

Rigidly secured in the bushing member 47 is an up wardly extendingcylindrical thin metal sleeve 50 which slidably receives the enlargedlower portion of driving plunger 25, said sleeve being formed with avertical slot 51 to provide clearance for pin 28. As shown in FIGURE 2,sleeve 50 terminates below the top end of slot 29 to allow pin 28 to beelevated above said sleeve, whereby to permit rotation of the assembly43 when it is being removed from or inserted in the apparatus.

Secured on the top end of plunger element 44 is a head member 52 havinga frusto-conical top portion 53 snugly receivable in the tapered boreportion 27 of member 25. A locking bolt 54 extends through the bore ofmember 25 and is threadedly engageable in the top end of head member 52,said bolt being provided with the knurled head 55 which bears againstthe top rim of shank portion 26 to allow head member 52 to be drawntightly into the tapered bore portion 27, whereby to lock plungerelement 44 to the driving plunger 25.

A vertical cover cap 56 is threadedly engaged in an upstanding collar 57integrally formed on a bracket plate 58 secured on the top wall ofhousing portion 19, the collar 57 being coaxial with the driving plunger25 and the cap 56 being of sufficient height to allow vertical movementof the driving plunger through its full upward stroke. The cap 56 isreadily removable to provide access to the knurled head 55.

When the subassembly 43 is to be removed, the plunger 25 is firstelevated so that pin 28 is in an elevated position clear of sleeve 50,as shown in dotted view in FIGURE 2. Cap 56 is then removed and bolt 54.is unscrewed, untastening head 52. The subassernbly 43 is then rotatedby means of knurled member 68 through a sufficient angle to bring thevertical portion of slot 48 into alignment with pin 49. The subassemblycan then be moved downwardly and withdrawn from the housing portion 20.A replacement subassembly 43 may be attached to the titration apparatusby following a reverse procedure.

In inserting a replacement subassembly 43, rotation thereof to bring thepin 49 substantially into contact with the closed end of the horizontalportion of slot 48 automatically vertically aligns slot 51 with pin 28.In this position, the frusto-conical portion 53 of head member 52 willbe closely received in the tapered bore portion 2'] so that it can besubsequently locked tightly thereagainst by means of the locking bolt54.

The cylindrical lower portion of head member 52 has secured thereon acollar member 70 of resilient deformable material which slidably engagesthe inside surface of sleeve member '3 and acts to maintain the headmember 52 in a centered position therein.

The plunger element 44 is of constant-cross-sectional area cylindricalshape and may be made of suitable stable plastic material, such asVycor, or the like. The plunger element is advanced into the reservoir45 by means of the precision screw member 26, displacing a volume oftitrant linearly related to the screw advance. The digital counter 40provides digital read-out in volumetric units of titrant dispensed.

While a specific embodiment of an improved titration apparatus has beendisclosed in the foregoing description, it will be understood thatvarious modifications within the spirit of the invention may occur tothose skilled in the art. Therefore it is intended that no limitationsbe placed on the invention except as defined by the scope of theappended claims.

What is claimed is:

1. In a titration apparatus of the character described, a support, avertical tubular housing secured to said support, a hollow drivingplunger slidably mounted in said tubular housing, a dispensing pipette,cooperating pin and bayonet slot means detachably connecting saidpipette to the bottomend of said housing, said driving plunger having abottom recess, a plunger element sealingly and slidably received-in saidpipette, a head member on said plungerelement closely fitting andreceived in said recess, and removable bolt means extending from the topof the housing substantially through the entire length of said hollowdriving plunger and secured to said head memher, said bolt means causingthe head member to be drawn tightly into said recess and to rigidly lockthe plunger element to the driving plunger.

2. In a titration apparatus of the character described, a support, avertical tubular housing secured to said support, a hollow drivingplunger slidably mounted in said tubular housing, a dispensing pipette,a supporting bushing, means sealingly securing said pipette to saidsupporting bushing, said bushing being formed at its top end with agenerally L-shaped slot, an inwardly projecting locking pin in the lowerportion of said housing, said bushing being engageable in said lowerhousing portion with the pin lockingly engaged with said L-shaped slot,whereby to detachably connect said pipette to the bottom end of saidhousing, said driving plunger having a bottom recess, a plunger elementsealingly and slidably received in said pipette, a head member on saidplunger element closely fitting and received in said recess, andremovable bolt means extending from the top of the housing substantiallythrough the entire length of said hollow driving plunger and secured tosaid head member, said bolt means causing the head member to be drawntightly into said recess and to rigidly lock the plunger element to thedriving plunger.

3. In a titration apparatus of the character described, a support, avertical tubular housing secured to said support, a hollow drivingplunger slidably mounted in said tubular housing, a dispensing pipette,a supporting bushing, means sealingly securing said pipette to saidsupporting bushing, said bushing being formed at its top end with agenerally Lshaped slot, an inwardly projecting locking pin in the lowerportion of said housing, said bushing being engageable in said lowerhousing portion with the pin lockingly engaged with said L-shaped slot,whereby to detachably connect said pipette to the bottom end of saidhousing, said driving plunger having a bottom recess, a plunger elementsealingly and slidably disposed in said pipette, a head member on saidplunger element closely fitting and received in said recess, and aheaded bolt having its shank portion extending from the top of thehousing substantially through the entire length of said hollow drivingplunger and being threadedly engaged with said head member, said boltcausing the head member to be drawn tightly into said recess and torigidly lock the plunger element to said driving plunger.

4. In a titration apparatus of the character described, a support, avertical tubular housing secured to said support, a hollow drivingplunger slidably mounted in said tubular housing, a dispensing pipette,a supporting bushing, means sealingly securing said pipette to saidsupporting bushing, said bushing being formed at its top end with agenerally L-shaped slot, an inwardly projecting locking pin in the lowerportion of said housing, said bushing being engageable in said lowerhousing portion with the pin lockingly engaged with said L-shaped slot,whereby to detachably connect said pipette to the bottom end of saidhousing, said driving plunger having a downwardly flaring substantiallyfrusto-conical bottom recess, a plunger element sealingly and slidablydisposed in said pipette, a head member on said plunger element having afrusto-conical top portion closely fitting and received in said recess,and a headed bolt having its shank portion extending through said hollowdriving plunger and being threadedly engaged with said head member.

5. In a titration apparatus of the character described, a support, avertical tubular housing secured to said support, a hollow drivingplunger slidably mounted in said tubular housing, a dispensing pipette,a supporting bushing, means sealingly securing said pipette to saidsupporting bushing, said bushing being formed at its top end with agenerally L-shaped slot, an inwardly projecting looking pin in the lowerportion of said housing, said bushing being engageable in said lowerhousing portion with the pin lockingly engaged with said L-shaped slot,whereby to detachably connect said pipette to the bottom end of saidhousing, an upstanding sleeve element secured in said bushing and beingreceived in said housing around said driving plunger, outwardlyprojecting guide pin means on said plunger, said sleeve element and saidhousing being formed with registrable vertical slots through which saidguide pin means extends, to limit relative rotation of said drivingplunger with respect to said sleeve element, the vertical slot in saidsleeve element being open at its top end, said driving plunger beingmovable at times to a position wherein said guide pin means is locatedabove said sleeve element, whereby to allow such relative rotation atsaid times, said driving plunger having a bottom recess, a plungerelement sealingly and slidably disposed in said pipette, a head memberon said plunger element closely fitting and received in said recess, andremovable bolt means extending through said hollow driving plunger anddetachably secured to said head member.

6. The structure of claim 5, and wherein said bolt means comprises aheaded bolt having its shank portion extending through said hollowdriving plunger and being threadedly engaged with said head member.

7. The structure of claim 6, and wherein the means sealingly securingsaid pipette to said supporting bushing includes an externally knurledclamping ring threadedly engaged on the lower portion of the bushing.

8. A pipette and dispensing plunger attachment for a titration apparatuscomprising an annular supporting bushing having an enlarged externallythreaded lower portion,

a pipette having an annular top sealing flange disposed in said enlargedlower portion, an externally knurled clamping ring threadedly engaged onsaid enlarged lower portion, sealing means between said clamping ringand said sealing flange and between said sealing flange and saidenlarged lower portion cooperating with said clamping ring to sealinglysecure said flange in said enlarged lower portion, the upper portion ofsaid bushing being formed with a generally L-shaped slot open at its topend, a plunger element sealingly and slidably extending through saidsealing means between the sealing flange and the enlarged lower portion,said plunger element extending into said pipette, said plunger elementhaving an upwardly tapering frusto-conical top end and being internallythreaded at said last-named top end, an upstanding sleeve elementsecured in said bushing, said sleeve element being formed with avertical slot open at its top end, and a headed anchoring boltthreadedly engaged in said last-named top end.

References Cited by the Examiner UNITED STATES PATENTS 325,642 9/85VJorthen 222-567 X 2,765,955 10/56 Natelson 22232 2,925,198 2/60 Healey22232 2,946,486 7/60 Gilmont 222-38 LOUIS J. DEMBO, Primary Examiner.

1. IN A TITRATION APPARATUS OF THE CHARACTER DESCRIBED, A SUPPORT, AVERTICAL TUBULAR HOUSING SECURED TO SAID SUPPORT, A HOLLOW DRIVINGPLUNGER SLIDABLY MOUNTED IN SAID TUBULAR HOUSING, A DISPENSING PIPETTE,COOPERATING PIN AND BAYONET SLOT MEANS DETACHABLY CONNECTING SAIDPIPETTE TO THE BOTTOM END OF SAID HOUSING, SAID DRIVING PLUNGER HAVING ABOTTOM RECESS, A PLUNGER ELEMENT SEALINGLY AND SLIDABLY RECEIVED IN SAIDPIPETTE, A HEAD MEMBER ON SAID PLUNGER ELEMENT CLOSELY FITTING ANDRECEIVED IN SAID RECESS, AND REMOVABLE BOLT MEANS EXTENDING FROM THE TOP